Dust test results on multicontact, circuit board connectors

A study to determine if the normal force of a connector is a factor in maintaining a low contact resistance after an accumulation of dust on the pins and receptacles is discussed. A dust mixture of hygroscopic salts and natural mineral particles was used. The test connectors included the standard Metral connector with a nominal normal force of 0.55 N, a special Metral connector with an extra-low normal force of 0.35 N, and a 963C connector with a normal force of about 1.5 N. The dust accumulation during the test was estimated to be equivalent to a minimum of 20 years in an indoor environment such as a telephone central office. It is shown that the Metral connector design, with a specified minimum contact normal force of 0.45 N, will maintain a stable connection resistance even when severely contaminated with dust. The Metral connector design still functions reliably at a normal force of 0.35 N, demonstrating that the standard design possesses adequate margin with respect to performance when contaminated with dust